The present invention relates to a method and device for the controlled and sustained release of chlorine dioxide gas.
Chlorine dioxide in low concentrations, i.e. up to 1,000 ppm, has long been recognized as useful as an antimicrobial and as a deodorant. In the presence of relatively low concentrations of chlorine dioxide, odiferous chemicals are oxidized to compounds which have essentially no odor. Such compounds include, for example, aldehydes, amines and thiols which are oxidized respectively to alcohols or acids, nitro compounds or various intermediates such as nitroso compounds, and to disulfides or oxides of sulfur. At higher levels than required for deodorizing, chlorine dioxide may act as an antimicrobial.
Its use is particularly advantageous for use where it is desirable to reduce the antimicrobial population and reduce noxious odors on and around foodstuffs for several reasons. First of all, chlorine dioxide generation does not result in the noxious byproducts such as chloramines or chlorinated organic compounds that can be produced when elemental chlorine is utilized for the same or similar purposes. Secondly, it chlorine dioxide gas is also generally considered to be safe for human contact at concentrations considered to be effective for deodorization and most antimicrobial applications because such concentrations are generally low.
There are several methods which have been suggested for generation of chlorine dioxide. One method is to use a solid mixture of a metal chlorite and an acid in a liquid, aqueous environment. A second method combines a metal chlorite and a solid acid where chlorine dioxide gas is released under dry conditions. A third system employs the combination of a metal chlorite and a solid organic anhydride to generate a high concentrated flow of chlorine dioxide which must be diluted with a constantly flowing stream of inert gas.
Such solid reagent systems, however, have a couple of disadvantages. Typically, upon mixing there is a sudden, highly concentrated stream of chlorine dioxide generated, and the mixture of reactants, if not properly contained and kept moisture free, produce chlorine dioxide prematurely reducing the shelf life of the reactants.
Methods for the controlled release of chlorine dioxide gas have been developed for purposes of both deodorization and for reduction of microbial populations.
For instance, U.S. Pat. No. 6,238,643 describes a method of producing an aqueous solution of chlorine dioxide from the reaction of a metal chlorite and an acid forming component which do not react to produce chlorine dioxide in the substantial absence of water. The reactants are separated from liquid water by a membrane which allows the controlled passage of liquid water and/or water vapor into contact with the reactants. The chlorine dioxide thus generated passes out through the membrane into the liquid water to produce the desired aqueous solution.
U.S. Pat. No. 6,077,495 describes a method, composition and system for generating chlorine dioxide gas in a controlled release manner by combining at least one metal chlorite and a dry solid hydrophilic material that reacts with the metal chlorite in the presence of water vapor, but does not react with the metal chlorite in the substantial absence of liquid water or water vapor to produce chlorine dioxide gas in a sustained amount of from about 0.001 to 1,000 ppm.
U.S. Pat. No. 5,091,107 describes methods and devices for the production of controlled quantities of chlorine dioxide at concentrations which are effective to function as a deodorant or a germicide whereby aqueous chlorite compositions such as aqueous sodium chlorite are brought into contact at a controlled rate through capillary means, e.g. a wick with an absorbent pad containing acid or other reactant which will react with the chlorite and form chlorine dioxide.
However, in each of the above described methods, it is still difficult to maintain a sustained release of chlorine dioxide over a period of time.
The present invention relates to a method, composition and device for the controlled and sustained release of chlorine dioxide over a period of time.
More specifically, the present invention relates to a method of generating an antimicrobially active gas including the steps of providing a dry solid composition which reacts in the presence of water or water vapor to the gas, but does not react in the absence of water or water vapor, and exposing the composition to a moist environment.
The composition is divided into a plurality of separate portions, each of which is contained in a separate sealed compartment of a unitary container housing. The sealed compartments are sequentially unsealed to expose the contents to the environment around the container housing in response to a predetermined stimulus event.
The release of the gas can be controlled and sustained using the method, composition and device of the present invention.
The present invention, in another embodiment relates to a device for the generation of an antimicrobially active gas including a unitary container housing having a plurality of sealed compartments each of which contains a composition which will gradually release chlorine dioxide upon exposure to moist air, a compartment opener operable on the unitary container housing to open a compartment in sequence in response to an opening signal and a controller operable to periodically issue a opening signal to the opener.
The reactants may be in solid form. If it is in solid form, only a single compartment is required. The reactants may also be in liquid form, or one reactant may be a liquid and one reactant a solid. If at least one reactant is in liquid form, a barrier may be provided between the reactants, thus requiring two compartments be opened in order to allow the reactants to mix.
In one embodiment, the present invention relates to a device and method for the controlled and sustained release of an antimicrobially active gas including a power supply, an electrical switch, a plurality of conductors, a controller and a container having a top and bottom and housing a plurality of sealed pockets. Each pocket contains the gas generating composition of the present invention. The conductors are connected to the electrical switch and each terminate in an electrode. Each electrode is attached to a sealed pocket. The controller is operatively connected to the power supply and to the electrical switch, and is capable of directing the switch to apply power sequentially to each conductor for a first predetermined time interval. There is a second predetermined time interval between each application of power to each conductor.
Using the device as described above allows for sequentially supplying power to each of the conductors for a first predetermined time interval such that the sealed pockets may be opened sequentially. There is a second predetermined time interval between each application of power to each conductor.
Upon application of power to the conductors and thus to each electrode, the sealed pockets open, exposing the contents to atmospheric moisture thereby initiating the gas generating reaction.